On Wed, 19 Feb 2020 09:46:56 +0800
Ming Lei [off-list ref] wrote:

On Tue, Feb 18, 2020 at 8:35 PM Halil Pasic [off-list ref] wrote:

quoted

On Tue, 18 Feb 2020 10:21:18 +0800
Ming Lei [off-list ref] wrote:

quoted

On Thu, Feb 13, 2020 at 8:38 PM Halil Pasic [off-list ref] wrote:

quoted

Since nobody else is going to restart our hw_queue for us, the
blk_mq_start_stopped_hw_queues() is in virtblk_done() is not sufficient
necessarily sufficient to ensure that the queue will get started again.
In case of global resource outage (-ENOMEM because mapping failure,
because of swiotlb full) our virtqueue may be empty and we can get
stuck with a stopped hw_queue.

Let us not stop the queue on arbitrary errors, but only on -EONSPC which
indicates a full virtqueue, where the hw_queue is guaranteed to get
started by virtblk_done() before when it makes sense to carry on
submitting requests. Let us also remove a stale comment.

The generic solution may be to stop queue only when there is any
in-flight request
not completed.

I think this is a pretty close to that. The queue is stopped only on
ENOSPC, which means virtqueue is full.

quoted

Checking -ENOMEM may not be enough, given -EIO can be returned from
virtqueue_add()
too in case of dma map failure.

I'm not checking on -ENOMEM. So the queue would not be stopped on EIO.
Maybe I'm misunderstanding something In any case, please have another
look at the diff, and if your concerns persist please help me understand.

Looks I misread the patch, and this patch is fine:

Reviewed-by: Ming Lei <redacted>

Thank you very much!

Regards,
Halil

Thanks,
Ming Lei